Blasting operations frequently trigger a series of explosions in an exact order, with precise timing. For this purpose, blasting apparatuses can employ electronic detonators that may be initiated to fire in response to electrical signals transferred thereto by signal transmission lines. Typically, electronic detonators are positioned as desired to form a blasting array, each being connected to a blasting machine. The blasting machine may communicate directly with a single detonator or multiple detonators in the array via selected signal transmission lines (including for example trunk lines and/or branch lines or by wireless communications means). Communication signals may include, but are not limited to, ARM, DISARM, and FIRE signals, and may also include security code information such as firing codes to prevent inadvertent or illicit detonator initiation.
Safety and reliability are paramount for any blasting apparatus, and efficient detonator initiation is an important factor in this regard. Detonators that fail to initiate result in unexploded charges at the blast site, with inevitable safety concerns. Moreover, the reliable initiation of detonators is imperative to ensure that the required blasting pattern is properly effected.
Electronic detonators typically comprise an elongated, often cylindrical casing. At one end of the casing is a percussion-actuation end comprising a flat, shaped or hemispherical surface. Adjacent the surface is positioned a base charge. The signal transmission line enters the detonator casing at a signal input end of the detonator usually opposite the percussion-actuation end. The detonator casing may also house various components required for proper signal processing and detonator control. For example, such components may include, but are not limited to, one or more printed circuit boards, means for signal processing, means for storing detonator firing code information, and means for arming, disarming and initiating firing of the base charge.
Signal transmission lines may transmit signals between a blasting machine and one or more detonators via electrical communication. Alternatively, signal transmission lines may extend from components of a wireless detonator assembly (e.g. a wireless signal transmission or receiving means) to the main detonator unit, thereby to transmit electronic signals to or from the detonator and other wireless assembly components. In any event, signal transmission lines generally include two (or more) wires in juxtaposition. Each wire must be connected to the detonator for proper operation thereof. Moreover, each signal transmission line is preferably suited for two-way communication between the blasting machine and the detonator. In this way, the status of individual detonators as well as firing codes and logging information, can be monitored by an associated blasting machine.
Traditionally, the wires of the signal transmission lines are soldered directly to circuit elements of signal processing means retained within the detonator shell. Such signal processing means may include, but are not limited to, printed circuit boards (PCBs), which may be involved in receipt, analysis, processing or relay of the incoming signal(s). In this way, the wires from the signal transmission line enter into the detonator shell at the signal input end of the detonator.
For example, U.S. Pat. No. 6,085,659 issued Jul. 11, 2000, discloses an electronic explosives initiating connector which includes a firing element which has a designed no-fire voltage and an operating circuit which operates at any voltage in a range of voltages that straddles the no-fire voltage. The connector pertains to an electronic detonator including a housing for containing the primary explosive and other components for detonator operation. The detonator includes a header and an integrated circuit, which together function to process incoming signals from a signal transmission line. The housing is crimped at one end to a crimp plug. Electrical leads extend from the integrated circuit through the crimp plug and to the exterior of the detonator to form the signal transmission line. The presence of the crimp plug in the detonator system of U.S. Pat. No. 6,085,659 acts as a seal to protect the components inside the housing against the ingress of moisture and dirt.
Whilst simple to manufacture, such ‘traditional’ detonator-to-signal transmission line connections present several disadvantages. One particular disadvantage lies in that the wires from the signal transmission line must be properly installed (e.g. by soldering) to the internal components of the detonator in the factory production line setting, and the detonator/signal transmission line assemblies must be shipped accordingly. It is noteworthy that each detonator may be selected from a variety of detonators (for example each having different delay periods or security functions), and each signal transmission line may comprise a desired length. As a result, a large number of possible detonator/signal transmission line combinations are possible, thereby increasing the costs and logistics of product transportation and storage of a range of commercial products.
In another disadvantage, the wires of the signal transmission line are soldered directly onto the printed circuit board or related components of the detonator initiation system. For this reason, the wire/detonator connection can be prone to breakage particularly if tensile or tugging forces are applied to the signal transmission line. Such forces may impose directly on the wire/detonator connection at the printed circuit board. The resulting disruption or breakage of the corresponding contacts can result in detonator failure in the field, with inevitable safety concerns.
To overcome at least some of the disadvantages of the prior art, “modular” detonator systems have been developed that include, for example, plug and socket means or junction boxes to allow positive attachment of signal transmission lines to detonators at the blasting site. In this way, the detonators (including the base charges) can be shipped to a customer and conveyed to the blasting site separately from the signal transmission lines. This results in improved safety and logistics of transporting and handling the components of the blasting apparatus.
For example, related U.S. Pat. No. 5,392,712 (issued Feb. 28, 1995), U.S. Pat. No. 5,585,591 (issued Dec. 17, 1996), and U.S. Pat. No. 5,596,164 (issued Jan. 21, 1997) disclose a detonator assembly for use with a booster charge. The assembly includes an electrical detonator and two electrical leads of equal length. One end of each lead is connected to the electrical detonator, and the other end of each lead is connected to a connector. The connector capable of maintaining the ends of the two electrical leads in non-conductive condition, and this allows the splicing of an additional leg wire thereto without the use of stripping or crimping tools. In this way, the desired length of wire can be spliced to the detonator assembly in the field. Moreover, the detonators may be conveniently packaged for transportation and storage.
In another example, U.S. Pat. No. 6,655,289 issued Dec. 2, 2003 discloses trigger units for initiating pyrotechnic elements, which usually consist of a switch and control unit, ignition means and an ignition charge body. The invention pertains to the use of a switch and control unit surrounded by a first shell, wherein the first shell is connected to a second shell, which contains the ignition charge body. The design is suited to efficient automatic assembly. In specific embodiments, the patent discloses a plug and socket system for the attachment of signal transmission lines to detonators. The detonator may include a percussion-actuation end and a plug located at the opposite end from the percussion-actuation end. The plug includes pins extend from the detonator, and which include connections to the printed circuit board. Importantly, the pins are adapted for engagement with a corresponding plug socket located at the end of a signal transmission line.
The safety of blasting apparatuses, and in particular electronic blasting apparatuses, is of paramount importance. There remains a continual need to develop electronic blasting apparatuses that include features that improve both reliability and safety. This need especially extends to the integrity of the blasting network, and communication between the components of the network. Most particularly, the connections between the signal transmission lines and the detonators encompass a key feature of the blasting network. Poor or weak connections can result in a failure to initiate specific detonators or groups of detonators within a blasting network, with deleterious effects upon the blasting sequence and the overall blasting event.